What Is the Difference Between a Leech and a Blood Sucker?

The main difference between a leech and other critters considered bloodsuckers is species. Leeches are unique because they are worms that live in wet, watery areas. Leeches are creepy, yet fascinating, because they release a toxin into their prey that acts as a numbing agent, allowing them to feed without being discovered. It's hard to escape leeches because they have two suckers on each end of their bodies.